1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to devices and methods for limiting and/or preventing deposits on a streamer used underwater during marine seismic surveys, and, more particularly, to mounting a fast fastening antifouling tape or substrate on streamers before and/or after protuberances.
2. Discussion of the Background
In the oil and gas industry, geophysical surveys are used to evaluate underground formations both on land and offshore. An image of the explored underground formation is generated based on seismic reflections from a formation's layer interfaces, detected by seismic receivers towed concurrently with a seismic source.
Seismic exploration campaigns may last long periods (e.g., several months). Preferably, during these campaigns, the streamers remain in the water (except, for example, in cases of extreme unfavorable weather conditions) because recovering/deploying them is expensive and tedious. While the streamers are immersed in seawater for several consecutive months, at a shallow depth (a few meters), and dragged at a low speed (less than or equal to 5 knots), the streamers' outer surfaces are subject to fouling, particularly due to the proliferation of microorganisms (i.e., bio-fouling). One of the most common types of microorganisms attaching to streamers is the barnacle, which adheres permanently to a hard substrate, either by growing its shells directly onto the substrate or by means of a stalk. The biofouling first occurs in turbulence areas where there is a protuberance on the streamer (e.g., a bird collar or weigh mounted thereon). For example, FIG. 1 illustrates barnacle 10 growing in abundance in locations at which diameter varies in longitudinal direction, a portion 20 having a larger diameter than the adjacent portions 30 and 40 of the streamer.
In time, bio-fouling results in substantial disadvantages such as:    (1) generating hydrodynamic flow noise;    (2) amalgams or incrustations forming on the streamer's outer surfaces, which are likely to disturb seismic measurements;    (3) increasing drag on the streamers and, consequently, increasing fuel consumption to tow them;    (4) a strong, unpleasant stench developing within a few days when streamers covered with biofouling are recovered and exposed to air; and    (5) the streamer's outer shell being pierced by certain types of biofouling, resulting in water intake inside the streamer.
Several techniques have been applied conventionally to address the biofouling problem. For example, a cleaning device with rotary brushes and/or blades may be temporarily or permanently attached on streamers to clean their outer surfaces. The use of cleaning devices is impeded by the presence of protuberances on the streamers, often resulting in a more effective cleaning exactly where most needed, near protuberances. Although cleaning devices continue to be subject to research and improvement, their practical value (reliability versus cost) remains unsatisfactory.
Another conventional technique used to address the biofouling problem involves using antifouling paints (also used on boat hulls). However, “antifouling” paints generally contain tributyltin (TBT), which is toxic. Such antifouling paints are therefore used with caution, from an environmental standpoint, to minimize seawater pollution. The safe use of antifouling paints is also problematic for the persons likely to be in contact with TBT during the manipulation of seismic streamers. Furthermore, techniques for applying “antifouling” paint are hardly compatible with technical and economical constraints linked to seismic streamers; painting them is a long and costly operation due to the streamer's length. In addition, to allow the paint to dry (to minimize seawater pollution), the painted seismic streamers have to be stored in a manner that requires a considerable amount of space, which is not economically viable onboard a vessel.
Accordingly, it would be desirable to provide devices, systems, and methods addressing the biofouling problem of streamers used in marine seismic explorations in an economically attractive manner while avoiding the afore-described problems and drawbacks.